Planar balun and multi-layer circuit board
The present invention provides a planar balun and a multi-layer circuit board. The planar balun formed on the multi-layer circuit board comprises: a first winding with at least one turn, which is formed in a first conductive layer, and has a first lead and a second lead serving as a first balanced end and a second balanced end of the balun respectively; a second winding with at least one turn, which is formed in a second conductive layer separated from the first conductive layer by at least a first insulating layer, and has a third lead and a fourth lead, wherein the third lead is connected to a ground potential, and the fourth lead serves as an unbalanced end of the balun; and a first balancing capacitor, which is connected between a selected portion near a center of the first winding and the ground potential.
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This application claims priority to Chinese Patent Application No. 201611269648.4, filed on Dec. 30, 2016, the entirety of which is incorporated herein by reference.
BACKGROUNDThe present invention relates to the technical field of radio frequency circuits, and in particular to a planar balun and a multi-layer circuit board on which the planar balun is formed.
In a radio frequency power amplifier, a push-pull circuit may generally be used, such as a power amplifier in which two transistors operate in a push-pull manner. In the push-pull circuit, a balun (balanced-unbalanced converter) is an essential component. For example, it can convert, at an input stage, a signal on an unbalanced transmission line into two balanced inputs with the same power but opposite phases to provide to the transistors of the power amplifier, and convert, at an output stage, two balanced outputs of the power amplifier into an unbalanced (single end) output in an opposite manner so as to provide the unbalanced output to an unbalanced load.
As an example,
In the circuit in
Depending on different operational frequencies, the balun, such as the one shown in
In a push-pull amplifier of an MR (magnetic resonance) detection system, due to a low operational frequency (tens to hundreds MHz) and high power, a balun made of ferrite material is generally used. However, since the ferrite material may form magnetic saturation, which results in that such structure cannot be used in a strong magnetic environment of a scan room of the MR detection system, it must be placed outside the scan room and connected to the MR detection system via cable. This results in a high transmission loss, and also goes against to system integration.
To this end, there is a need for a balun which is suitable to be used in strong magnetic field environment, such as a scan room of an MR detection system.
SUMMARYOne exemplary embodiment of the present invention provides a planar balun formed on a multi-layer circuit board, the balun comprising: a first winding with at least one turn, which is formed in a first conductive layer, and has a first lead and a second lead serving as a first balanced end and a second balanced end of the balun respectively; a second winding with at least one turn, which is formed in a second conductive layer separated from the first conductive layer by at least a first insulating layer, and has a third lead and a fourth lead, wherein the third lead is connected to a ground potential, and the fourth lead serves as an unbalanced end of the balun; and a first balancing capacitor, which is connected between a selected portion near a center of the first winding and the ground potential.
Another exemplary embodiment of the present invention provides a multi-layer circuit board, on which the planar balun as mentioned above is formed.
The planar balun and multi-layer circuit board in the embodiments of the present invention are suitable for use in a strong magnetic field environment such as a scan room of an MR detection system, and can have an improved balance.
Other features and aspects will be apparent through the following detailed description, figures and claims.
The present invention will be better understood in light of the description of the exemplary embodiments of the present invention with reference to the accompanying drawings. In the drawings, the same or similar drawing reference represents the same or similar components, in which:
Hereafter, a detailed description will be given for preferred embodiments of the present disclosure. It should be pointed out that in the detailed description of the embodiments, for simplicity and conciseness, it is impossible for the description to describe all the features of the practical embodiments in details. It should be understood that in the process of a practical implementation of any embodiment, just as in the process of an engineering project or a designing project, in order to achieve a specific goal of the developer and in order to satisfy some system-related or business-related constraints, a variety of decisions will usually be made, which will also be varied from one embodiment to another. In addition, it can also be understood that although the effort made in such developing process may be complex and time-consuming, some variations such as design, manufacture and production on the basis of the technical contents disclosed in the disclosure are just customary technical means in the art for one of ordinary skilled in the art associated with the contents disclosed in the present disclosure, which should not be regarded as insufficient disclosure of the present disclosure.
Unless defined otherwise, all the technical or scientific terms used in the claims and the description should have the same meanings as commonly understood by one of ordinary skilled in the art to which the present disclosure belongs. The terms “first”, “second” and the like in the description and the claims of the present utility model do not mean any sequential order, number or importance, but are only used for distinguishing different components. The terms “a”, “an” and the like do not denote a limitation of quantity, but denote the existence of at least one. The terms “comprises”, “comprising”, “includes”, “including” and the like mean that the element or object in front of the “comprises”, “comprising”, “includes” and “including” covers the elements or objects and their equivalents illustrated following the “comprises”, “comprising”, “includes” and “including”, but do not exclude other elements or objects. The term “coupled” or “connected” or the like is not limited to being connected physically or mechanically, nor limited to being connected directly or indirectly.
According to an embodiment of one aspect of the present invention, a planar balun is provided. The balun of this embodiment is formed on a multi-layer circuit board, comprising a first winding with at least one turn, which is formed in a first conductive layer, and has a first lead and a second lead serving as a first balanced end and a second balanced end of the balun respectively; a second winding with at least one turn, which is formed in a second conductive layer separated from the first conductive layer by at least a first insulating layer, and has a third lead and a fourth lead, wherein the third lead is connected to a ground potential, and the fourth lead serves as an unbalanced end of the balun; and a first balancing capacitor, which is connected between a selected portion near the center of the first winding and the ground potential.
Preferably, in the example in
Those skilled in the art will appreciate that, although
The number of turns of the second winding may be determined according to application requirements and various design factors. For example, a desired impedance transformation ratio may be achieved by reasonably setting the number of turns of the winding. When the balun with a desired impedance transformation ratio serves as, for example, the input balun and/or output balun in the push-pull circuit in
In addition, those skilled in the art will appreciate that, although
The first winding and second winding may be formed in, for example, a conductive layer (such as a copper layer) of a PCB substrate by using an approach such as etching. Those skilled in the art will appreciate that any appropriate method or process in the prior art may be used to form the first winding and the second winding, and this is not described in detail herein.
In order to enable the balun to operate at a desired frequency, in this example, as shown in
In order to improve the balance of the balun, preferably, the first winding and the second winding are respectively formed as a substantially symmetrical pattern or layout.
By reasonably designing the wiring patterns (such as the wiring length, width, intervals between turns) of the first winding and the second winding, the balun can operate at different operational frequencies when different capacitance values are chosen for the tuning capacitors C1 and C2. That is, on the premise of not changing the wiring pattern, the balun can operate in different operational frequencies by only choosing tuning capacitors C1 and C2 with different capacitance values. For example, with regard to different applications of 1.5 T (Tesla) and 3 T in an MR detection system, the balun in this embodiment may respectively operate around 63.86 MHz and 127.72 MHz (or 128 MHz) by choosing tuning capacitors C1 and C2 with different capacitance values. Such balun facilitates mass production and improves the production efficiency.
In a preferred embodiment, a plurality of candidate portions may be provided near the center of the first winding, for example,
Similarly,
The balun in this embodiment is particularly suitable for, for example, a push-pull amplifier in an MR detection system. Due to the existence of, for example, the first balancing capacitor Cb1 shown in
More specifically, when the balun of this embodiment serves as the input balun 1 (the second winding as a primary coil and the first winding as a secondary coil) in
By virtue of the structures described with reference to
In one preferred embodiment, a regulating capacitor may be connected between the first lead and the second lead of the first winding and the ground potential in
Optionally, in order to shield the interference from surrounding circuit components, a grounding welding pad which matches the outer contour of the winding can be provided at the periphery of the first winding and the second winding. As examples,
In one preferred embodiment, the balun formed on a multi-layer circuit board may further comprise a metal ground serving as the ground potential, which is formed in a third conductive layer separated from the first conductive layer of the first winding and the second conductive layer of the second winding.
As an example, the first conductive layer and the second conductive layer can be spaced by a first insulating layer and a second insulating layer, and the third conductive layer with the formed metal ground can be located between the first insulating layer and the second insulating layer. That is, the multi-circuit board on which the balun is formed can comprise the first conductive layer, the first insulating layer, the third conductive layer, the second insulating layer and the second conductive layer in sequence from top to bottom (or from bottom to top).
For another example, the first conductive layer and the second conductive layer can be spaced by a first insulating layer, and the third conductive layer with the formed metal ground can be formed as in a layer separated from the first conductive layer or the second conductive layer by at least a second insulating layer.
In a first exemplary structure of
Note that for the simplicity of the drawings, in the conductive layers of
Preferably, as shown in
For example, when the balun is mounted to a water cooling board for heat dissipation, generally a groove needs to be opened on the water cooling board to avoid the balun position, thereby avoiding the electro-magnetic interference between the metal water cooling board and the balun. However, by utilizing the present embodiment, the balun having the metal ground shown in
With regard to the operational frequency of 63.86 MHz,
Similarly, with regard to the operational frequency of 128 MHz,
It can be seen from the simulation results from
According to another aspect of the present invention, a multi-layer circuit board is provided, on which the planar balun described above with reference to
Some exemplary embodiments have been described in the above. However, it should be understood that various modifications may be made thereto. For example, if the described techniques are carried out in different orders, and/or if the components in the described system, architecture, apparatus or circuit are combined in different ways and/or replaced or supplemented by additional components or equivalents thereof, proper results may still be achieved. Accordingly, other implementation also falls within a protection range of the claims.
Claims
1. A planar balun formed on a multi-layer circuit board, comprising:
- a first winding with at least one turn, which is formed in a first conductive layer, and has a first lead and a second lead serving as a first balanced end and a second balanced end of the balun respectively;
- a first peripheral grounding pad formed at a periphery of the first winding, the first peripheral grounding pad matching an outer contour of the first winding;
- a second winding with at least one turn, which is formed in a second conductive layer separated from the first conductive layer by at least a first insulating layer, and has a third lead and a fourth lead, wherein the third lead is connected to a ground potential, and the fourth lead serves as an unbalanced end of the balun;
- a second peripheral grounding pad formed at a periphery of the second winding, the second peripheral grounding pad matching an outer contour of the second winding; and
- a first balancing capacitor, which is connected between a selected portion near a center of the first winding and the ground potential.
2. The planar balun of claim 1, wherein the selected portion is determined from a plurality of candidate portions near the center of the first winding according to an operational frequency of the balun.
3. The planar balun of claim 1, further comprising:
- a first regulating capacitor, which is connected between a portion near the first lead of the first winding and the ground potential; and
- a second regulating capacitor, which is connected between a portion near the second lead of the first winding and the ground potential.
4. The planar balun of claim 1, further comprising a first tuning capacitor, which is connected between the first lead and the second lead.
5. The planar balun of claim 1, further comprising a second tuning capacitor, which is connected between the fourth lead and the ground potential.
6. The planar balun of claim 1, wherein the first winding and the second winding are formed at corresponding positions of the first conductive layer and the second conductive layer, and overlapped with each other.
7. The planar balun of claim 1, wherein the first lead and the second lead are oriented in a first direction, and the fourth lead is oriented in a second direction which is opposite to the first direction.
8. The planar balun of claim 1, further comprising a metal ground serving as the ground potential, which is formed in a third conductive layer separated from the second conductive layer by at least a second insulating layer.
9. The planar balun of claim 1, further comprising a metal ground serving as the ground potential, which is formed in a third conductive layer separated from the first conductive layer by at least a second insulating layer.
10. The planar balun of claim 8, wherein a coverage area of the metal ground is greater than or equal to respective coverage areas of the first winding and the second winding.
11. The planar balun of claim 1, wherein the first winding is a single-turn winding.
12. The planar balun of claim 11, wherein the second winding is a multi-turn winding, with a terminal of the innermost turn of the second winding being connected to the third lead, and a terminal of the outermost turn of the second winding being connected to the fourth lead.
13. The planar balun of claim 12, wherein the first balancing capacitor is connected between a selected portion near an inner center of the single-turn winding and the ground potential, and there is a center tap at an outer center of the single-turn winding, the center tap being connected to the ground potential via the second balancing capacitor.
5451914 | September 19, 1995 | Stengel |
5917386 | June 29, 1999 | Dobrovolny |
6917254 | July 12, 2005 | Kaehs |
7656247 | February 2, 2010 | Kaehs |
7902939 | March 8, 2011 | Blair |
8618802 | December 31, 2013 | Albrecht et al. |
20080024241 | January 31, 2008 | Hata |
20150042340 | February 12, 2015 | Zeng et al. |
202135098 | January 2012 | CN |
202135098 | February 2012 | CN |
- Jafari et al., A Wideband Compact Planar Balun for UHF DTV Applications, 2009, Journal of Electromagnetic Waves and Applications, vol. 23, 8 pages. (Year: 2009).
Type: Grant
Filed: Dec 21, 2017
Date of Patent: Mar 17, 2020
Patent Publication Number: 20180191326
Assignee: General Electric Company (Schenectady, NY)
Inventors: Yu Liu (Beijing), Dongliang Yang (Beijing), Xin Xie (Beijing), Haoyang Xing (Beijing), Kai Wang (Beijing), Chunlai Xiao (Beijing)
Primary Examiner: Dean O Takaoka
Application Number: 15/851,037
International Classification: H03H 7/42 (20060101); H01P 5/10 (20060101); H01F 27/28 (20060101); H01F 17/00 (20060101); H01F 27/40 (20060101); H01F 27/29 (20060101);